Method of die-casting screws by using screw coils



1963 KAZUO KANEKO ETAL 3,112,540

METHOD OF DIE-CASTING SCREWS BY USING SCREW COILS Filed June 8, 1960 United States Patent 3,112,540 METHOD OF DIE-CASTING SCREWS BY USING SCREW COILS Kazuo Kaneko and Chuyo Hisatsune, Nagoya-shi, Takeo Kuwako, Hiratsuka-shi, and Tatsuo Kobayashi, Fujisawa-shi, Japan, assignors to Kobe Steel Works, Ltd., a corporation of Japan, Chuyo Hisatsune, and The Yokohama Rubber Company, Limited, a corporation of Japan, jointly Filed June 8, 1960, Ser. No. 34,772 Claims priority, application Japan June 12, 1959 1 Claim. (Cl. 22-203) This invention relates to methods for die casting material onto a coil member to form a hollow internally threaded element.

Methods of die-casting threaded elements by utilizing a threaded core and a cooperating coil are known, but a method whereby threaded elements high in precision can be mass-produced, has not been achieved.

It is an object of the invention to set forth a method whereby threaded elements high in accuracy can be mass produced.

It is a further object of the invention to use a threaded core element in the production of the threaded element containing the insert member in which the core element can be reused in subsequent casting processes.

It is a still further object of the invention to utilize the coil itself to protect the core element against thermal effects of the molten cast metal.

In the production of precision cast elements with threaded insert members, it is of extreme importance that the core on which the insert is initially threaded be easily removed from the coil after the material has been cast thereon without damaging the threads in the coil or the threads on the core.

In the case of die-casting, the metal to be die cast will be in a molten state at a high temperature and often it will be under high pressure. If the threaded portion of the core contacts the molten metal, severe damage is inflicted o the threads such that when the core is removed from the cast metal the core will not be reusable with other coils for subsequent casting operation.

It is a feature of the present invention that the coil itself protects the threads of the core by completely covering the same and extending beyond the end of the core. It is a further feature that the end of the coil that projects beyond the core becomes embedded in the cast metal so as to improve the anchoring of the coil in the cast metal.

In accordance with the method of the invention, a coil member having internal and external threads is threaded onto an internal core. The coil member is longer than the core, so as to cover the same and extend therefrom. Notches are formed in the external threads of the coil member. The core and the coil member threaded thereon are next fixed in a mold and molten metal is injected under pressure into the mold. The coil member, by virtue of the longer length thereof, prevents contact between the molten metal and the threads of the core from the metal which is injected into the mold so as to thermally insulate the latter threads all along the length of the core. The molten metal solidifies on the coil to form the threaded element and thereafter the core is removed from the threaded element by unscrewing the core therefrom.

The other features, objects and advantages of the present invention will become clear from the following explanation of the present invention with reference to the drawings, wherein FIGURE 1 is a sectional view of a mold for injection molding in which a core is threaded into a coil, and

FIGURE 2 is a sectional view of the completed threaded element with coil therein as produced in the mold in FIG. 1.

Patented Dec. 3, 1963 In FIGURE 1 there is shown a core pin 1 supporting a screw coil 2. The coil pin 1 is divided into a precisely core 1 are substantially impenetrable to molten metal. The fitting part of the core to the die is so designed as to prevent the core from floating out during die-casting. Coil 2 is so dimensioned that, when fitted on the screw The strength of the cast part and particularly the uniting of the screw coil with the cast material are determined by layers 7. In die-casting, when the melt is poured into die cavity 8,

difference between the melt and the die and core.

The inner surface of the die is painted with a die casting agent to permit removal of the solidified cast material therefrom. According to the present invention, the length of the screw coil is made larger than that of the threaded rectly the threaded portion of the core so that the core may be easily pulled out after die-casting and be undamaged.

FIGURE 2 shown in section the threaded element produced in the mold in FIGURE 1.

By making the length of the screw coil larger than the length of the threaded portion of the core, the coil protects the threads of the core in that the adiabatically expanded melt forming layer 7 will not directly contact the threaded part of the core.

What is claimed is:

A method of die casting a threaded element comprising threading a coil member having internal and external threads on a threaded core, said coil member being longer than said core so as to cover the same and extend therefrom, the coil member being formed with notches in the external threads thereof, fixing the core and coil member in a mold, injecting molten metal under pressure into said mold, said coil member preventing contact between the molten metal and the threads of the core to thermally insulate said latter threads all along the length of the core from said molten metal, the molten metal solidifying on the coil to form said threaded element, and removing the core from said threaded element.

References Cited in the file of this patent UNITED STATES PATENTS 

